The battle is on for France's opposition party to find a successor to Nicolas Sarkozy to unite the divided right and return it to power.

The centre-right UMP party is looking for a charismatic leader who can rally support after losing its 17-year hold on the presidency to Socialist François Hollande in May.

Several former ministers had suggested they would stand as party general secretary, but after weeks of speculation the field was reduced to just two when the deadline for nominations closed last week.

Now the former prime minister François Fillon, 58, and his younger rival Jean-François Copé, 48, the current party chief, will go head to head for the job.

The two men claim to be natural successors to Sarkozy, with whom both had an uneasy, at times hostile, relationship in recent years.

Fillon, a discreet and serious character whose wife is Welsh, is seen as an experienced, safe pair of hands. He was appointed PM in 2007 after helping Sarkozy win his presidential election bid.

Defying frequent reports that he was to be replaced in a reshuffle, Fillon remained at Matignon (the prime minister's official residence) throughout Sarkozy's five-year term in office.

Copé, once sidelined by Sarkozy as a potential rival, was brought back to his inner circle as head of the UMP in 2010. Unashamedly ambitious and seen as more charismatic and hyperactive than his rival, he is presenting himself as Sarkozy Mark II, telling supporters he will "walk in the footsteps" of the former president.

"France needs someone who is going to jump in and get their hands dirty," he said recently. He added he would step down if Sarkozy decided to return to mainline politics.

Fillon said he too would remain close to Sarkozy: "I cannot imagine leading the party he helped to develop without his support," Fillon told the daily Le Parisien.

In a swipe at Copé he added: "The truth is that Sarkozyism is a bit like love; there are those who speak a lot about it because they have reason to do so. Their love is fairly recent, while there are others who over the years can prove their love."

Both are keen to play up links to Sarkozy after an opinion poll by LH2 published on Tuesday found that 43% of rightwing voters think Sarkozy would have the best chance of regaining the presidency for the UMP party in 2017, ahead of Fillon, with 32%, and Cope, with 21%.

However, polls give Fillon a considerable lead over Copé, which the younger candidate will hope to close in the coming weeks.

In policy terms, less divides Fillon and Copé, who have similar views on economics and Europe. Both support tighter budget discipline and reforms to lower employment charges.

Last week, there was a brief spat between both camps over the number of supporters each had among card-carrying UMP members.

On Tuesday, Copé announced with great fanfare that he had amassed 30,000 signatures. Within hours the Fillon camp responded by announcing its candidate had at least 45,000. A member of Copé's team said the news had fallen on the candidate like "a thump on the head".

The only woman who had been seriously in the running, former environment minister Nathalie Kosciusko-Morizet, who was Sarkozy's spokesperson during his election campaign,was in third position but stood down at the last minute.

"Many of our supporters were hoping for a third way so the election didn't end up being a duel between Jean-François Copé and François Fillon," she told French journalists. "It's not necessarily such a good image for our party," she added.

NKM, as she is known, refused to say who she would support.

The candidates will officially begin their campaigns on 5 October and party members will vote on a new leader on 18 November.

Copé will publish his campaign programme on 3 October, entitled Manifesto for an Uninhibited Right. "Those who read it will see what I have in my heart," he said, adding that it contained some "suggestions to shock".

The highlight of the campaign will be a televised debate. Copé has welcomed the chance to go face-to-face live with his rival, but Fillon's camp has been more cautious.

"A debate in the same political family is always a little complicated," said Fillon's campaign director Eric Ciotti.